1. Field of the Invention
The present invention relates to a copper alloy and a method of manufacturing the same, and more particularly to a copper alloy used for an electronic component and a method of manufacturing the same.
2. Description of the Background Art
In recent years, a device to which a lead frame or a connector is to be applied has been more miniaturized and multifunctional, and also a packing density has become higher. Accordingly, a lead frame on which an integrated circuit (IC) is mounted has become thinner, the number of pins serving as terminals of a connector used in an electronic device has increased, and the pitch between the pins has become smaller. For those reasons, there is an increasing demand for reliable connection in packaging.
More specifically, miniaturization of an electronic component requires improvement of strength of a metal material used for the electronic component. Also, as a cross-sectional area of a terminal becomes smaller because of increase in the number of pins and reduction in the pitch between the pins, a metal material for an electronic component having more excellent electrical conductivity is required.
To meet the foregoing requirements, according to the conventional practices, an alloy formed by adding beryllium (Be) to copper (Cu) was employed. Such alloy has both tensile strength equal to or higher than 800 MPa (mega pascal) and conductivity equal to or higher than 50% IACS (international annealed copper standard).
However, considering the recent environmental issues, a current trend is to avoid use of the above-mentioned conventional material containing beryllium. Thus, an attention is now being drawn to a Cu—Ni—Si alloy (so-called Corson alloy) in place of the conventional material containing beryllium.
It is known that a Cu—Ni—Si alloy is a precipitation hardened alloy which is hardened by virtue of micro crystals of a Ni2Si intermetallic compound which are dispersed and precipitated out in Cu and serve as barriers against transformation. Many reports about efforts to increase strength and conductivity by controlling an amount of Ni (nickel) and Si (silicon) to be added or a ratio of Ni to Si have so far been made.
For example, Japanese Patent Application Laid-Open No. 10-152736 (which will hereinafter be referred to as “JP No. 10-152736”) discloses in FIG. 2 a technique of forming a copper alloy having conductivity equal to or higher than 50% IACS and tensile strength equal to or higher than 700 MPa by carrying out cold rolling and aging on a raw material containing Ni of 1.0 to 5.0 percent by mass, Si of 0.2 to 1.0 percent by mass, Zn (zinc) of 0.3 to 0.5 percent by mass, and P (phosphorus) of 0.03 to 0.3 percent by mass, in which a mass ratio of Ni to Si is controlled to be in a range of 4.5 to 5.5.
Also, Japanese Patent Application Laid-Open No. 2001-49369 (which will hereinafter be referred to as “JP No. 2001-49369”) discloses in FIG. 1 a technique of forming a copper alloy containing Ni of 1.0 to 4.8 percent by mass, Si of 0.2 to 1.4 percent by mass, and inclusions each being equal to or smaller than 10 μm in size, in which alloy the number of the inclusions each being in a range of five to ten u m in size is smaller than 50/mm2 per section of the copper alloy taken along a direction of rolling.
However, according to the above-described technique disclosed in JP No. 10-152736, though the formed copper alloy has conductivity higher than 50% IACS, the tensile strength thereof is approximately 740 MPa (N/mm2) at the highest. On the other hand, according to the above-described technique disclosed in JP 2001-49369, though the tensile strength of 770 MPa (N/mm2) is achieved, a copper alloy having conductivity higher than 50% IACS cannot be formed.
As is made clear from the above description, it was difficult to obtain a copper alloy which does not contain Be and has both tensile strength equal to or higher than 800 MPa and conductivity higher than 50% IACS by the conventional techniques.